Dropping temperatures, snow showers and cold northerly winds have ushered in Old Man Winter. The apple and peach trees have dropped their leaves which signals the trees have entered dormancy. Dormancy is period of rest that fruit trees enter to protect themselves from the cold temperatures and allows the trees to survive the winter. Dormancy is essential for the health and development of fruit trees. It protects the tree’s susceptible organs, like bud meristems (growth structure for the new crop cycle), from temperature injuries.
Fruit trees go through three physiological stages of dormancy: acclimation, endo-and eco-dormancy and deacclimation. For those of us who are not biologists or horticulturalists, it is better to try to keep things simple and not get too technical.
Acclimation is the period of time when the tree stops growing and gets ready for freezing temperatures. This happens after the fruit has ripened and has been harvested. As the days grow shorter there is a gradual period of cooling before the first hard freeze. Full acclimation is usually reached in late October and early November.
Once fruit trees reach full dormancy, they enter the next stage of physiological dormancy which is endo-dormancy or a period of chilling hours accumulation. Chilling temperatures are not freezing temperatures but temperatures between 32 and 45 degrees. Once the amount of chilling temperatures is satisfied, the fruit trees go into the eco-dormancy period. This is the time when the tree is just waiting for warmer temperatures to stimulate spring growth.
As temperatures get warmer and reach above 40 degrees the trees start to wake up and break out of dormancy. This is deacclimation. The flowering buds can tolerate some frost and light freezing at this time but when the flowers are fully open frost and freezing temperatures are not welcome.
As orchardists, dormancy is important to us as this is the time when we pull out the pruning equipment and get started with the annual process of maintaining our trees. When pruning, our objectives are to regulate tree growth, increase yields, improve fruit size and quality and maintain plant health and vigor.
As one season ends and another begins, we again want to thank all those who supported our “growing business.” Wishing everyone the best during the upcoming holidays.